muscovy feed hack--toss eaten cobs of corn to them and attract flies

I noticed cobs of corn I'd eaten and tossed on the ground had a load of flies on them, and threw them to the muscovies.  At first they didn't pay attention to them, but later they all gathered around it like a buffet at rush hour and chowed down.  (The flies had scattered when I picked it up but I imagine a bunch had started to gather).  

There's a chance of flies carrying botulism, but I would think that's only if there's soured feed around.  You could toss pits of fruit instead and attract fruit flies, I dont' know if they bother with anything that small though.